Synthesis, structure and photo-physical properties of phosphorus-supported fluorescent probes

Various phosphorus-supported fluorescent probes have been synthesized by the condensation reaction of multi-functional phosphorus hydrazides with various fluorophore-containing carboxaldehydes. Compounds, thus prepared, in this study are (PhO)2P(O)[N(Me)–Ndouble bond; length as m-dashCH–R] (1a, 1b), Ph2P(O)[N(Me)–Ndouble bond; length as m-dashCH–R] (2b, 2c, 2d), PhP(O)[N(Me)–Ndouble bond; length as m-dashCH–R]2 (3b, 3c), P(S)[N(Me)–Ndouble bond; length as m-dashCH–R]3 (4b, 4c), P(O)[N(Me)–Ndouble bond; length as m-dashCH–R]3 (5a, 5b, 5c), N3P3(O2C12H8)2[N(Me)–Ndouble bond; length as m-dashCH–R]2 (6a, 6b, 6c), N3P3(O2C12H8)[N(Me)–Ndouble bond; length as m-dashCH–R]4 (7a, 7b, 7c, 7d) and N3P3[N(Me)–Ndouble bond; length as m-dashCH–R]6 (8b, 8c), where R=1-pyrenyl (a), 9-anthracenyl (b), 9-phenanthryl (c) and 7-(N,N′-diethylamino)-3-coumarinyl (d). All of these compounds have been characterized by various analytical techniques including 31P{1H} NMR spectroscopy. Compounds 1b, 2b, 3b, 4b, 5b, 5c and 6d have also been characterized by single crystal X-ray analysis. All of these phosphorus-supported compounds exhibit excellent fluorescence properties in aqueous solution at near physiological conditions.